It is conventionally known that a variable gear ratio steering (VGRS) device is capable of varying a ratio of a steered angle relative to a steering angle of a steering device. According to the following patent document 1, for example, a differential wheel mechanism and a variable gear ratio device are directly coupled to a shaft of a steering wheel provided as a steering device. The variable gear device has a gear ratio control motor, which drives the differential gear mechanism. It is recently also known that an electric power steering (EPS) device is used together with the VGRS apparatus as a mechanism for assisting steering operation of a vehicle. The electric power steering apparatus is operated electrically to generate torque.    (Patent document 1) JP 2008-273327A
In the gear mechanism of the VGRS apparatus, vibration sometimes occurs due to manufacturing error of gears. In case the VGRS apparatus is provided to the shaft of the steering wheel, vibration caused by meshing of gears is directly transferred to the steering wheel. As a result, a driver is likely to feel uncomfortable.